1. Field of the Invention
The present invention relates to a method for preparing needle-like, fibrous or porous diamond, or an aggregate thereof.
2. Discussion of Background
By virtue of its excellent properties such as extremely high hardness, heat conductivity, modulus of elasticity and chemical stability, diamond is expected to have a wide range of applications. However, the practical application is presently rather limited mainly because the technology for the synthesis has not yet been adequately developed to have the morphology, texture or function required for particular purposes. If it is possible to synthesize needle-like, fibrous or porous diamond, or an aggregate thereof, such diamond may be used as a filler material in combination with metals, plastics, ceramics and various other materials to obtain composite materials, whereby it will be useful in various fields as a material having excellent mechanical and thermal properties such as high strength, high abrasion resistance and high thermal conductivity.
Heretofore, for the synthesis of needle-like or fibrous diamond, a method has been known wherein a transition metal powder such as iron or nickel is utilized in a chemical vapor deposition method or a plasma-assisted vapor deposition method developed by the present applicant. This is a method wherein a gas mixture of a hydrocarbon and hydrogen is excited and dissociated by heated filaments, by high frequency plasma or by microwave plasma, so that needle-like or fibrous diamond is precipitated on a substrate on which a transition metal powder is deposited (Japanese Unexamined Patent Publication No. 158195/1987). No other methods have been known. Further, no method has been known for the production of porous diamond.
It is an object of the present invention to provide a method for readily and efficiently produce needle-like, fibrous or porous diamond, or an aggregate thereof in a manner which is fundamentally different in the principle from the above-mentioned conventional methods.